Greetings, we praise God before you, other than Whom there is no deity. Praise be to God Who has broken your enemy, the obstinate tyrant who had leapt upon this community, stripped it of its authority , plundered its fay and seized control of it without its consent. Then he had killed the choice members of it and had preserved the wicked members of it. He made the property of God a state (divided) among its tyrants and wealthy. He was destroyed as Thamud were destroyed. (Now) there is no Imam over us.

Therefore come; through you, may your God unite us under truth. Al Numan Ibn Bashir is in the governor’s palace and we do not gather with him for the Friday (service). Nor do we accompany him (out of the mosque) for the Festival service. If we learn that you will come to us, we will drive him away until we pursue him to Syria, if God the Exalted, wills.

Imam Husayn's (a.s.) reply was as follows:

In the name of God, the Merciful, the Compassionate

From al Husayn Ibn ‘Ali, to the leaders of the believers and the Muslims

Hani and Said have brought me your letters; they are the last two of your messengers who have come to me. I have understood everything which you have described and mentioned. The (main) statement of your great men is: “There is no Imam over us. Therefore come; through you, may God unite us under truth and Guidance.”

I am sending you my brother, Muslim Ibn Ail, who is my cousin and my trustworthy (representative) from my House. If he writes to me that the opinions of your leaders and the men of wisdom and merit among you is united in the same way as the messengers who have come to me have described and as I have read in your letters, I will come to you speedily, God willing. For by my life, what is the Imam except who judges by the Book, one who upholds justice, one who professes the religion of truth, and one who dedicates himself to the essence of God.

Greetings.

(The two letters can be found in Tabari, Volume 19, The Caliphate of Yazid Ibn Muawiya, pages 25 - 26, English Version. SUNY Press. Copied from Kitab al Irshad, pages 301 and 303)